\[ -\left (y'(x)-1\right )^2+e^{-2 x} y'(x)^2+e^{-2 y(x)}=0 \] ✗ Mathematica : cpu = 300.86 (sec), leaf count = 0 , timed out
$Aborted
✓ Maple : cpu = 0.614 (sec), leaf count = 65
\[ \left \{ y \left ( x \right ) =x+\ln \left ( {\frac {1}{{{\rm e}^{x}}} \left ( -1-\sqrt { \left ( {{\rm e}^{x}} \right ) ^{2}-{\frac { \left ( {{\rm e}^{x}} \right ) ^{2}}{ \left ( {{\rm e}^{{\it \_C1}}} \right ) ^{2}}}} \right ) } \right ) +{\it \_C1},y \left ( x \right ) =x+\ln \left ( {\frac {1}{{{\rm e}^{x}}} \left ( -1+\sqrt { \left ( {{\rm e}^{x}} \right ) ^{2}-{\frac { \left ( {{\rm e}^{x}} \right ) ^{2}}{ \left ( {{\rm e}^{{\it \_C1}}} \right ) ^{2}}}} \right ) } \right ) +{\it \_C1} \right \} \]